Mark, mine had two, inline 30A fuses that were hidden behind the visible fuse panel. If either one of them are blown, the converter will not charge the battery, but will seem to work normally otherwise. Have you checked those two fuses?
If those fuses check good too, then I suspect you'll just have to get a new converter. The Elixir converter is no longer manufactured, so you'll need to get a different brand.
Look at the "sticky" in this section to see the brand I want with and my writeup on how to wire it in. I believe the other brand that is recommended is mentioned in that thread too.
Hi-Lo 1707T - Tire Minder TPMS on Tow Vehicle and Trailer, 300W Solar Battery Charger, Equal-i-zer WDH
2014 F150 Platinum 4x4 3.5L EcoBoost SCrew